In Reaction Turbines, There is no sudden pressure drop. There is a gradual pressure drop and takes place continuously over the fixed and moving blades. A number of wheels are fixed to the rotating shaft. Fixed guide ways are provided in between such pair of rotating wheels.
The function of fixed blades (F) is that they guide the steam as well as allow it to expand in a larger velocity. It is similar to nozzles as in case of Impulse Turbine.
The moving blades serve the following functions :
* It converts the Kinetic energy of the steam into useful mechanical energy.
* The steam expands while flowing over the moving blades and thus gives reaction to the moving blades. Hence, The turbine is called as Reaction Turbine.
* The Velocity of the steam decreases as the kinetic energy of the steam absorbed. '
* The velocity of the steam decreases as the kinetic energy of the steam absorbed.
Since the pressure of steam reduces continuously as it follows over the moving blades, the volume of steam increases at lower pressures. Therefore, the diameter of the reaction turbine must increase after each group of blade rings. It may be noted that, because of the small pressure drop in each stage, the number of stages required in a reaction turbine is much greater than an impulse turbine of the same power output.
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